Japanese Unexamined Patent Publication No. 2006-269520 (Patent literature 1) or United States Patent No. 7741201 (Patent literature 2) corresponding to it discloses a gate stack structure formed by interposing a titanium film as a buffer layer between a high-k gate insulation film and a titanium nitride gate electrode.
Japanese Unexamined Patent Publication No. 2006-245306 (Patent literature 3) discloses a technology that makes it possible to reduce damages to a gate insulation film and obtain a gate electrode having an appropriate work function by forming a titanium nitride gate electrode by CVD (Chemical Vapor Deposition) at 450° C. or lower.